Fe-based amorphous magnetic powder, magnetic powder core with excellent high frequency properties and method of making them

ABSTRACT

The present invention provides an amorphous alloy powder and magnetic powder cores exhibiting excellent high frequency properties and a method for making themof. The composition of said alloy powder by atomic percentage satisfies the following formula: (Fe 1-x M x ) 100-a-b-c P a T b D c , wherein M represents at least one element of Co and Ni; T is over three elements selected from Al, C, B and Si, D is at least one element of Sn, Cr, Mn, Mo, W, V, Nb, Ta, Ti, Zr, Hf, Pt, Pd and Au; the subscripts x, a, b, and c satisfy the relationships 0.01≦x≦0.16, 8≦a≦15, 10≦b≦25 and 0.5≦c≦6. The said amorphous alloy powder is made by atomization method and a magnetic powder core comprises a molded article of mixture of the said alloy powder and an insulating material. A method of making the amorphous alloy powder core includes the steps of screening, insulating, compacting, annealing and spray painting.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.11/558,478 filed Nov. 10, 2006, which claims priority to Chinese PatentApplication No. 200510114933.4 filed Nov. 16, 2005, both of which areincorporated by reference herein.

RELATED TECHNICAL FIELD

The present invention relates to a Fe-based amorphous alloy powder, andmore particularly, relates to an amorphous soft magnetic alloy powdercore manufactured by said amorphous alloy powder and a method for makingthemof.

ART OF BACKGROUND

Fe-based amorphous and nanocrystalline line soft magnetic alloy, forinstance, amorphous Fe—Si—B series alloy disclosed by U.S. Pat. No.4,217,135 and Fe—Cu—M—Si—B series (wherein M is one of Nb, Mo, Hf, Ta,etc.) nanocrystalline soft magnetic alloy disclosed by U.S. Pat. No.4,881,989 have been widely used in various electronic parts andcomponents because of their excellent soft magnetic properties. Toobtain the said Fe-based amorphous alloy, a high cooling rate ofapproximately 10⁻⁵K/s is necessary. Though amorphous alloy ribbon can beproduced in large scale by single roller rapidly quenched technology, itis still difficult to obtain amorphous alloy powder directly from rapidquenching.

Fe-based amorphous and nanocrystalline alloy powder can be obtained bypulverizing ribbons, wherein the magnetic powder core can be obtained byseveral procedures such as sticking, pressing annealing and so forth.The problem of said magnetic powder core is that the powder obtained bypulverizing ribbons contains much deformed powder and the insulation ofthe powder is difficult, thus the core generally has low quality factor,high core losses.

Bulk amorphous Fe—Al—Ga—P—C—B—Si systems disclosed by U.S. Pat. No.5,876,519 have large glass formation ability, wherein the supercooledliquid region is over 50K, bulk amorphous alloy of 1.5 mm in thicknesscan be obtained by mold casting and the said alloy has excellent softmagnetic properties. By using the large glass formation ability of thesaid alloy system, amorphous powder can be prepared by atomizationmethod, wherein a magnetic powder core can be made thereof. The problemof said soft magnetic alloy powder is that, firstly, it containsexpensive element of Ga, which is difficult to popularize due to itshigh price; secondly, it does not contain antioxidation elements such asNi, Cr, therefore, antioxidation properties are poor and the powdereasily oxidates and its properties deteriorate while preparing powder byatomization method. Moreover, a Fe-based amorphous alloy systemdisclosed by Chinese Patent Publication No. CN1487536A at least containselements of P, C, B and a small amount of elements such as Cr, Mo, W, V,Nb, etc. Said alloy system contains only a small amount of antioxidationelement such as Cr and Mo etc, resulting in poor antioxidation abilityduring the process of atomization.

SUMMARY OF THE INVENTION

Accordingly, a primary object of the present invention is to provide anamorphous alloy powder with excellent high frequency properties, largeglass formation ability, low-cost and low oxygen content, and a methodfor making it.

Another object of the present invention is to provide a magnetic powdercore with excellent high frequency properties and method for making themthereof.

In order to achieve the objects mentioned above, the present inventioninvolves the following aspects:

In one aspect, the present invention provides an amorphous alloy powderwith excellent soft magnetic properties in high frequency. Thecompositions of said alloy powder by atomic percent satisfies thefollowing formula: (Fe_(1-x)M_(x))_(100-a-b-c)P_(a)T_(b)D_(c), wherein Mrepresents at least one element of Co and Ni; T is over three elementsselected from Al, C, B and Si; D is at least one element selected fromSn, Cr, Mn, Mo, W, V, Nb, Ta, Ti, Zr, Hf, Pt, Pd and Au. The subscriptsx, a, b, and c satisfy the relationships 0.01≦x≦0.16, 8≦a≦15, 10≦b≦25and 0.5≦c≦6. Preferably; 0.01≦x≦0.12, 9≦a≦12, 10≦b≦23 and 1≦c≦5,22≦(a+b+c)≦38.

The reduced glass transition temperature T_(rg) of said amorphous alloypowder satisfies T_(rg)≧0.53, wherein T_(rg)=T_(g)/T_(m), T_(g)represents glass transition temperature, T_(m) represents melting pointof alloy. The supercooled liquid region ΔT_(x)≧20K, whereinΔT_(x)=T_(x)−T_(g), T_(x) represents crystallization temperature. Theoxygen content of the powder is below 4000 ppm.

In another aspect, the present invention provides a method for making anamorphous alloy powder with excellent soft magnetic properties in highfrequency. The alloy components mentioned above are used to prepare thealloy powder by atomization method, wherein said atomization is wateratomization and/or gas atomization, while said gas atomization is one ofvacuum gas atomization, non-vacuum gas atomization, adjustable gasatomization or their combination.

The loose packed density of the powder ρ obtained by the process shouldsatisfy the relation: ρ≧2.4 g/cm³.

In the third aspect, the present invention provides an amorphousmagnetic powder core with excellent soft magnetic properties in highfrequency, comprising the components by weight percentage as follows:0.2%-7% of insulating agent, 0.01%-5% of adhesives, 0.01%-2% oflubricants, the rest is said amorphous alloy powder.

Wherein, said insulating agent is at least one selected from followinggroups of substances:

-   -   Oxide powder selected from SiO₂, CaO, Al₂O₃ and TiO₂,    -   Salts selected from silicates and phosphates,    -   Mineral powder selected from mica powder and kaolinite, and    -   surface film produced by chemical deposition or self-oxidation.

Said adhesives are organic adhesives and/or inorganic adhesives,wherein, the organic adhesives are at least one selected from epoxyresins, the inorganic adhesives are at least one selected fromphosphates.

Said lubricants are one or a combination selected from stearates andtalc powder.

The magnetic properties of said magnetic powder core shall satisfy therequirements of at least one, several or their combination of thefollowings:

-   -   Magnetic permeability is no less than 35;    -   Quality factor Q is not less than 30 at 1 MHz;    -   Per unit initial permeability is not less than 98% at 100 k Hz,        not less than 90% at 1M Hz;    -   Coercive force H_(c) corresponding with static magnetic        hysteresis loop in maximum magnetic field of 2000 A/m is below        70 A/m.

In the fourth aspect, the present invention provides a method for makingthe amorphous magnetic powder core with excellent soft magneticproperties in high frequency. Said method comprises the following steps:

(a) Using said amorphous alloy powder and a required content ofinsulating agent, adhesives and lubricants, mixing them and then dryingthem to obtain dry powder;(b) Compacting said dried powder under a pressure of 500 MPa-3000 MPa tomake magnetic powder core;(c) Annealing said molded magnetic powder core below the crystallizationtemperature of said amorphous powder.

After step (c), the process further including: (d) spray paintingmagnetic powder core and (e) testing the properties of magnetic powdercore.

In step (c), the temperature for annealing said magnetic powder core isbetween (T_(x)-100° C.) and T_(x), wherein T_(x) represents thecrystallization temperature of said alloy powder; annealing time is from5 minutes to 300 minutes; the atmosphere is one of vacuum, nitrogen andargon.

In step (c), the annealing temperature is between (T_(x)-70° C.) and(T_(x)-20° C.), wherein T_(x) represents the crystallization temperatureof said alloy powder.

The magnetic properties of magnetic powder core obtained by said processshall satisfy the requirements of at least one, or their combination ofthe followings:

-   -   Magnetic permeability is over 35;    -   Quality factor Q is not less than 30 at 1 MHz;    -   Per unit of initial permeability is not less than 98% at 100        kHz, not less than 90% at 1 MHz;    -   Coercive force H_(c) corresponding with static magnetic        hysteresis loop in maximum magnetic field of 2000 A/m is below        70 A/m.

To sum up, the present invention provides a technical solution formaking amorphous alloy powder and amorphous magnetic powder core,wherein the antioxidation properties and glass formation ability of thealloy are enhanced by the improvement of the components of the alloy,therefore, the amorphous alloy powder can be made by atomization method.Said powder is prepared into dried powder after insulating treatment andmixing with a small amount of adhesives, then molded into core. Afterproper heat treating, magnetic powder core can be obtained. The detailedprocedures will be described hereinafter.

Improvement of Alloy Composition

The iron element is the main component of the amorphous alloy powder ofthe present invention and a small amount of Co and Ni is includedthereof, so soft magnetic properties are improved and antioxidationproperties of powder are enhanced in the presence of Co and Ni;meanwhile the present invention contains more glass formation elementssuch as P, Al, C, B and Si, thus amorphous alloy powder is formed.Moreover, the present invention contains more than one kind of elementssuch as Sn, Cr, Mn, Mo, W, V, Nb, Ta, Ti, Zr, Hf, Pt, Pd, Au, etc.,which will further improve the glass formation ability of alloy andantioxidation properties. For instance, the glass formation ability isimproved in presence of the elements such as Sn, Zr, etc., and theaddition of Cr and Mo and some other elements can not only improve glassformation ability, but also enhance the antioxidation properties ofpowder as well.

In said amorphous alloy powder of the present invention, thecompositions of atomic percent of the alloy should satisfy the followingformula:

(Fe_(1-x)M_(x))_(100-a-b-c)P_(a)T_(b)D_(c)

Wherein M represents at least one element of Co and Ni; T is over threeelements selected from Al, C, B and Si; D is at least one elementselected from Sn, Cr, Mn, Mo, W, V, Nb, Ta, Ti, Zr, Hf, Pt, Pd and Au;and all by atomic percentage 0.01≦x≦0.16; 8≦a≦15; 10≦b≦25; 0.5≦c≦6.

As to the amorphous alloy powder of the present invention, the contentof Co and Ni is preferably from 1 at. % to 12 at. %; the content of P ispreferably from 9 at. % to 12 at. %; the content of Al, C, B and Si ispreferably from 10 at. % to 23 at. %; the content of Sn, Cr, Mn, Mo, W,V, Nb, Ta, Ti, Zr, Hf, Pt, Pd and Au is preferably from 1 at. % to 5 at.%.

As to the amorphous alloy powder of the present invention, the sum ofelements of Fe, Co and Ni is preferably from 62 at. % to 78 at. %; thesum of elements of P, Al, C, B, Si, Sn, Cr, Mn, Mo, W, V, Nb, Ta, Ti,Zr, Hf, Pt, Pd and Au is preferably from 22 at. % to 38 at. %.

The alloy of the present invention will inevitably contain a smallamount of 0 and other impurities, wherein the total quantity of theseimpurities is no more than 0.5 wt. %.

Preparation of Amorphous Alloy Powder by Atomization Method

The amorphous alloy powder of the present invention has large glassformation ability, so amorphous alloy powder can be prepared byatomization method; the supercooled liquid regionΔT_(x)≧20K(ΔT_(x)=T_(x)−T_(g), wherein T_(x) represents crystallizationtemperature and, T_(g) represents glass transition temperature, thereduced glass transition temperature T_(rg)≧0.53 (T_(rg)=T_(g)/T_(m),wherein T_(m) represents melting point of alloy).

The amorphous alloy powder of the present invention can be prepared bywater atomization method under non-vacuum condition, wherein the maximumparticle size of said amorphous alloy powder is greater than 75 μm andthe oxygen content of the powder is below 4000 ppm. The loose packeddensity of said water atomized amorphous alloy powder is characterizedin that, when the particle size is between −200 mess (about 74 μm) and+300 mess (about 49 μm), the loose packed density of powder is more than2.7 g/cm³; when the particle size is between −300 mess (about 49 μm) and+400 mess (about 38 μm), the loose packed density of powder is more than2.6 g/cm³; when the particle size is below −400 mess (about 38 μm) andover 5 μm, the loose packed density of powder is over 2.5 g/cm³.

In the present invention, the water atomized amorphous alloy powder isused to make magnetic powder core, wherein oxygen content is below 4000ppm. If the oxygen content is too high, magnetic properties of powderwill deteriorate. If properties of magnetic powder core prepared byusing said powder are not fine which results in the decrease ofpermeability and increase of coercive force of magnetic powder core.

In the present invention, the water atomized amorphous alloy powder isused to prepare a magnetic powder core, wherein the loose packed densityof the amorphous alloy powder is over 2.5 g/cm³. If the loose packeddensity is too small, properties of magnetic powder core will not befine. Too small loose packed density is generally resulted from smallparticle size of powder or complicated shapes of powder or much morepores contained in powder. The magnetic powder core prepared by usingsaid powder has the drawbacks of low density, large air gaps distributedin magnetic powder core, low magnetic permeability of powder core,larger coercive force and high core losses. The loose packed density ofamorphous alloy powder of the present invention is over 2.5 g/cm³,preferably over 2.8 g/cm³.

Compared with water atomization, gas atomization has lower cooling rate.In the alloy system of the present invention, the nearly ball-shapedamorphous alloy powder is made by vacuum gas atomization, non-vacuum gasatomization and adjustable gas atomization (a method that alloy liquidis atomized to prepare powder by gas and then the powder particles arecooled by water) and so on, wherein the particle size of said amorphousalloy powder is greater than 50 μm and the oxygen content of the powderis below 1500 ppm. The loose packed density of gas atomized amorphousalloy powder is over 3.5 g/cm³.

Magnetic Powder Core Prepared by Amorphous Alloy Powder

In the present invention, the gas atomized amorphous alloy powder isused to prepare magnetic powder core, wherein the oxygen content isbelow 1500 ppm. The magnetic powder core prepared by using saidamorphous alloy powder has good magnetic properties, high magneticpermeability and low coercive force. Compared with water atomizedpowder, magnetic powder core prepared by using gas atomized powder has ahigher cost and advanced properties, which will satisfy the requirementsof some high-level products.

The process for preparing magnetic powder core by using amorphous alloypowder of the present invention comprises the following steps:

1. Mixing the powder with insulating agent, adhesives and lubricant andthen drying them to made dried powder;2. Pressing the powder to form magnetic powder core;3. Annealing magnetic powder core;4. Spray painting magnetic powder core;5. Testing properties of magnetic powder core.

The amorphous alloy powder prepared is screened by test sieve, standardspanking vibration sieve, other types of vibration sieves and pneumaticpowder classifier equipments. Magnetic powder core is prepared accordingto the following steps:

Step 1

In order to increase the resistivity of the magnetic powder core, reduceeddy current losses and enhance magnetic permeability in high frequency,the present invention shall preferably select the following types ofinsulating agent and amorphous alloy powder to mix and insulate: 1.Oxide powder, such as SiO₂, CaO, Al₂O₃, TiO₂, etc., generally, oxidepowder has the advantages of stable properties, excellent properties ofinsulation and heat-resistance and low cost. 2. Silicates, phosphates,etc. 3. Other mineral powder such as mica powder, kaolinite, etc. 4.Surface film chemically formed or surface oxide occurred.

If said insulating agent is used to insulate the amorphous alloy powder,the weight percentage of insulating agent should be between 0.2 wt. %and 7 wt. % of the total mixture weight. If the insulating agent isless, the amorphous alloy powder will be difficult to be fullyseparated, thus resulting in more contact surface; if the insulatinglayer is too thin, the insulating layer between powder will easilybreakdown, losing insulating effect under the action of electromagneticinduction, causing larger losses of magnetic powder core and lowmagnetic permeability in high frequency. If too much insulating agent isprovided, the gap between powders will be too large, resulting in adecrease of magnetic permeability of the magnetic powder core. Theweight percentage of insulating agent more preferably is from 0.5 wt. %to 5 wt. %.

Molding properties of amorphous alloy powder are not good. The moldingof gas atomized powder is especially difficult. So the following typesof adhesive substances are preferable to serve as the adhesives for thepresent invention: 1. Organic adhesives, such as epoxy resin, which hasbeen commonly used in industrial product and the mixing with curingagent shall have better effect on sticking. 2. Inorganic adhesives, suchas phosphates, etc., inorganic adhesives have the advantages of goodheat-resistant properties and excellent insulation properties in itselfand dual functions of insulation and sticking, and an additional properamount will make the powder fully adhesive.

The content of adhesive shall not more than 5% of the total weight whileusing said adhesive materials. If too much adhesive is added, propertiesof magnetic powder core will deteriorate and so will magneticpermeability.

The mixture of lubricant functions as: 1. The powder is easy to flowwhile pressing the powder, thus increase the density of magnetic powdercore; 2. Magnetic core is not prone to stick with press mold, thusdemolding becomes easier. Stearates and talc powder is selectedpreferably as lubricant substances for the present invention, whereinthe weight is no more than 2 wt. % of total weight of mixture. If toomuch lubricant is added, the density of amorphous alloy powder inmagnetic powder core will decrease, resulting in the deterioration ofmagnetic properties and reduction of magnetic permeability.

In order to obtain fully insulated and mixed amorphous magnetic powderand excellent magnetic properties, the insulating substances, adhesivesand lubricants preferably occupy from 0.5 wt. % to 10 wt. % of totalweight of mixture for the present invention, more preferably from 1 wt.% to 7 wt. %.

Step 2

The molding pressure of the amorphous alloy powder of the presentinvention should be preferably from 500 MPa to 3000 MPa. If the pressureis less than 500 MPa, the powder will be difficult to mold or crackswill still exist after molding, the magnetic permeability will be lowand the properties of magnetic powder core will not be good. If thepressure is over 3000 MPa, the withstand pressure of mold will be large,thus the mold will be easily destroyed, and the powder will be difficultto insulate, losses of powder core will be high and the quality factorwill not be fine. The molding pressure of magnetic powder core is morepreferably from 800 MPa to 2500 MPa.

Step 3

The cooling rate of amorphous alloy powder is comparatively large duringthe preparation process, so stress will inevitably exist inside saidpowder; magnetic powder core shall have stress inside it while preparingunder the action of stirring and compression and these stress shallinfluence the properties of magnetic powder core. The internal stress ofpowder and magnetic powder core can be eliminated and the magneticproperties can be improved by annealing the amorphous magnetic powdercore. The temperature of annealing amorphous magnetic powder core shallsatisfy the requirements of: 1. Annealing temperature should be belowthe crystallization temperature of said alloy powder. Thecrystallization of amorphous alloy powder in said powder core results inmagnetic permeability and the increase in losses. 2. Annealingtemperature shall not be below (T_(x)-100° C.), wherein T_(x) representsthe crystallization temperature of said alloy powder. 3. The annealingtemperature of powder shall preferably be between (T_(x)-70° C.) and(T_(x)-20° C.). Since if the annealing temperature of the powder core istoo low, heat disturbance will be un-uniform, the internal stress inamorphous powder core will not be eliminated and the magnetic propertieswill not be fully enhanced.

The annealing time of amorphous powder core shall satisfy therequirements of: 1. The annealing time of powder core is less than 3hours since the manufacture cost will increase with too long annealingtime and low effectiveness. 2. The annealing time of the powder core ismore than 5 minutes since uniform treatment cannot be achieved whilebatch processing and the properties of powder core cannot be uniform ifthe annealing time is too short. 3. The annealing time of the powdercore shall preferably be between 30 minutes and 90 minutes. For thepresent invention, the annealing process mentioned above shouldpreferably be carried out in a protective atmosphere, which can bevacuum, hydrogen, nitrogen and argon atmosphere.

Step 4

In order to protect magnetic powder core from powder dropping and beingeroded by air and from the deterioration of magnetic properties, themagnetic powder core is protected by spray painting. The spray paintingmaterials shall preferably be of epoxy resin or a mixture of epoxy resinand estrodur compounds with relatively small curing stress. Thethickness of the spray painting is preferably from 50 μm to 300 μm.

Step 5

Various parameters of properties of amorphous magnetic powder core forthe present invention is tested respectively by the followingmethods: 1. Test method for inductance and quality factor Q, usingenameled copper wires with diameter of 0.2 mm to wind 10 turns uniformlyand to measure by Agilent 4294A precision impedance analyzer; magneticpermeability of magnetic powder core is calculated by the formula

${\mu_{e} = {\frac{\overset{\_}{l}\; L}{0.4\mspace{11mu} \pi \; N^{2}A} \cdot 10^{8}}},$

wherein l (unit is cm) represents average length of magnetic path, Nrepresents the turns of winding, A represents across section of magneticpath (unit is cm²). 2. Measuring static magnetic hysteresis loop ofmagnetic powder core by galvanometer, wherein the maximum magnetic fieldis 2000 A/m.

The magnetic powder core prepared by alloy powder of the presentinvention via said method has excellent soft magnetic properties in highfrequency. In detail, the properties of amorphous magnetic powder coresatisfy the following requirements: the quality factor is larger than 50and the magnetic permeability is larger than 40 at 500 kHz; the qualityfactor is larger than 30 and the magnetic permeability is larger than 40at 1 MHz; the quality factor of magnetic powder core is larger than 20and the magnetic permeability is larger than 40 at 3 MHz; while thedecrease of magnetic permeability should be less than 10% in thefrequency range from 100K to 1M.

The amorphous alloy prepared according to the technical solution of thepresent invention has large glass formation ability and goodantioxidation properties. Said alloy is characterized in large glassformation ability, good antioxidation properties and excellent softmagnetic properties. By preparing amorphous alloy powder with low oxygencontent via atomization method, the amorphous alloy powder withexcellent high-frequency magnetic properties, low oxygen content and lowcost and corresponding magnetic powder core can be obtained.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a photo of morphology of amorphous alloy powder havingcomposition of Fe₇₂Ni2Al₄Sn₂P₁₀C₂B₄Si₄ prepared according to embodiment1 of the present invention.

FIG. 2 is a graph illustrating an X-ray diffraction pattern of amorphousalloy powder having composition of Fe₇₂Ni2Al₄Sn₂P₁₀C₂B₄Si₄ preparedaccording to embodiment 1 of the present invention.

FIG. 3 is DSC thermogram of amorphous alloy powder having a compositionof prepared according to embodiment 1 of the present invention.

FIG. 4 is a graph illustrating the static magnetic hysteresis loop ofmagnetic powder core prepared according to embodiment 1 of the presentinvention with maximum magnetic field of 2000 A/m.

FIG. 5 is a graph illustrating the dependence of permeability onfrequency of an amorphous magnetic powder core prepared according toembodiment 1 of the present invention in different frequency.

FIG. 6 is a graph illustrating the dependence of quality factors onfrequency of an amorphous magnetic powder core prepared according toembodiment 1 of the present invention and of MPP magnetic powder core ascomparison in different frequency.

FIG. 7 is a graph illustrating the dependence of magnetic permeabilityon annealing temperature of an amorphous magnetic powder core preparedaccording to embodiment 5 of the present invention under differentannealing temperature at 100 kHz.

FIG. 8 is a graph illustrating the dependence of quality factor onannealing temperature of an amorphous magnetic powder core preparedaccording to embodiment 5 of the present invention under differentannealing temperatures at 100 kHz and 1 MHz.

FIG. 9 is a graph illustrating the dependence of coercive force H_(c) onannealing temperature corresponding with the static magnetic hysteresisloop of magnetic powder core prepared according to embodiment 5 of thepresent invention under different annealing temperatures in a maximummagnetic field of 2000 A/m.

EMBODIMENTS OF THE INVENTION Embodiment 1

In said embodiment, amorphous Fe₇₂Ni2Al₄Sn₂P₁₀C₂B₄Si₄ (compositionserial number is 1) alloy powder is prepared by water atomizationmethod. The raw materials shall be Fe, Ni, Al, Sn, P—Fe alloy, B—Fealloy, graphite and Si.

The morphology of the powder having composition ofFe₇₂Ni2Al₄Sn₂P₁₀C₂B₄Si₄ is shown in FIG. 1. As shown in this figure, thesmall particle powder is basically spherical, the big particle powder iselliptical and a small amount of powder is irregular.

The X-ray diffraction pattern of powder having composition ofFe₇₂Ni2Al₄Sn₂P₁₀C₂B₄Si₄ is shown in FIG. 2. As shown in this figure,distinct wide atlas exists in X-ray diffraction pattern and there is nonotable crystallization peak in it, which indicates that the alloypowder is amorphous. Thereby, Fe₇₂Ni₂Al₄Sn₂P₁₀C₂B₄Si₄ alloy can prepareamorphous alloy powder by water atomization method.

The DSC thermogram of Fe₇₂Ni2Al₄Sn₂P₁₀C₂B₄Si₄ powder is shown in FIG. 3.The speed is 10K/minute while performing DSC testing. As shown in thisfigure, alloy glass transition temperature T_(g) is 646K andcrystallization temperature T_(x) is 695K. The melting point T_(m)tested by high temperature DSC is 1209K, so we can calculate that thesupercooled liquid region of said alloy ΔT_(x) is 49K and the reducedglass transition temperature T_(rg) is 0.54.

The analysis of oxygen content of the powder indicates that the oxygencontent of the powder is 3500 ppm, which implies that alloy bearsstronger antioxidation properties and lower oxygen content.

The amorphous alloy powder of −300 mess obtained by screening isisothermal annealed for 30 minutes at a temperature of 440° C., whereinthe annealing process is in nitrogen atmosphere. Said amorphous alloypowder uniformly mixes with 1.5 wt. % of SiO₂ powder, 1 wt. % of epoxyresin and 0.3 wt. % of zinc stearate and then the mixture is dried inthe help of alcohol as a co-solvent. The molding of the magnetic powdercore is pressed under the pressure of 2 GPa. The magnetic powder core isannealed under vacuum condition. The annealing temperature is 400° C.and the annealing time is 90 minutes. The epoxy resin and estrodurcompounds are used to spray and paint the surface of magnetic powdercore. The thickness of the spray painting layer is 100 μm.

Static magnetic hysteresis loop of said magnetic powder core with themaximum magnetic field of 2000 A/m is shown in FIG. 4. As shown in thisfigure, magnetic powder core basically keeps constant permeabilityproperties within the range of testing magnetic field and coercive forceH_(c) is 45 A/m.

The measuring result of magnetic permeability of said magnetic powdercore is given in FIG. 5. As shown in this figure, magnetic permeabilityof said magnetic powder core is 46.9. With the increase of frequency,magnetic powder core keeps excellent constant permeability properties.Within the range of 6.3 kHz to 5 MHz, magnetic permeability drops from46.9 to 46.4. The percentage of dropping is less than 2%.

FIG. 6 shows the dependence of quality factor of said magnetic powdercore on frequency and the comparison example of FeNiMo magnetic powdercore is also shown. As shown in this figure, amorphous alloy magneticpowder core has higher quality factor in high frequency.

Embodiment 2

In said embodiment, amorphous Fe—Ni—Sn—Al—P—C—B—Si series alloy powderis prepared by water atomization method. The raw materials shall selectFe, Ni, Sn, Al, P—Fe alloy, graphite, B—Fe alloy and Si.

The nominal compositions of said embodiment are listed in Table 1. Glasstransition temperature of corresponding alloy, crystallizationtemperature, melting point, reduced glass transition temperature andwidth of supercooled liquid region are listed in Table 1 respectively.As seen from this table, except that composition 10 is in acrystallization process, alloy with other composition of said seriesalloy has high reduced glass transition temperature. The minimum is 0.54and the maximum is 0.58. The width of supercooled liquid region is over20K.

TABLE 1 Alloy composition in atomic No. percentage T_(g)/K T_(x)/KT_(m)/K T_(g)/T_(m) (T_(x) − T_(g))/K 1 Fe₇₂Ni₂Al₄Sn₂P₁₀C₂B₄Si₄ 646 6951209 0.54 49 2 Fe_(68.5)Ni₃Al₇P_(11.5)C₃B₅ 650 700 1209 0.54 50 3Fe₆₇Ni₇Sn₂Al₄P₁₀B₄C₂Si₄ 654 694 1208 0.54 40 4Fe_(70.5)Ni₁₀Sn₁Al₄P₁₃C₂B₃Si₆ 665 690 1204 0.55 25 5Fe₇₁Ni₄Sn₄Al₁P₁₀C₄B₂Si₄ 666 698 1206 0.55 32 6 Fe₇₂Ni₂Sn₁Al₃P₉C₂B₈Si₃675 703 1211 0.56 28 7 Fe₇₃Ni₁Sn₂Al₄P₁₀C₂B₄Si₄ 668 715 1202 0.56 47 8Fe_(73.5)Ni₂Sn₅P_(9.5)C₂B₅Si₃ 680 702 1200 0.57 22 9Fe_(74.5)Ni₁Sn₂Al₂P_(11.5)B₄Si₅ 698 729 1210 0.58 31 10Fe₇₇Ni₃Sn₁Al₃P₈C₂B₂Si₄ — — 1208 — — Comparative 1Fe_(68.5)Ni₃Al₇P_(11.5)C₃B₃Si₂ 652 700 1209 0.54 48

In the amorphous alloy powder with the composition mentioned above, theoxygen content and the loose packed density of amorphous alloy powder of−300 mess are listed in Table 2. As can be seen in this table, exceptfor the Comparison 1 of said series alloy, the loose packed density ofsaid series alloy is over 2.5 g/cm³ and the average oxygen content isbelow 3900 ppm, which implies that the alloy has stronger antioxidationproperties.

The amorphous alloy powder of −300 mess obtained by screening theamorphous alloy powder with the compositions mentioned above isisothermal annealed for 30 minutes at 440° C., wherein annealing processis in vacuum protection. Said amorphous alloy powder uniformly mixeswith 1 wt. % of SiO₂ powder, 1.5 wt. % of epoxy resin and 0.3 wt. % ofzinc stearate and then the mixture is dried in the help of alcohol asco-solvent. The mold magnetic powder core is pressed under the pressureof 2 GPa. The magnetic powder core is annealed under vacuum situation.The annealing temperature is 440° C. and annealing time is 60 minutes.The epoxy resin and estrodur compounds are used to spray and paint thesurface of magnetic powder core. The thickness of spray painting layeris 100 μm.

The properties of amorphous alloy powder core prepared by said methodmentioned above are also listed in Table 2, wherein the atomizationmethod is not suitable for Comparison 1, which will get the amorphousalloy powder with high oxygen content and low loose packed density. Itcan be concluded from Table 2 that the magnetic powder core made ofamorphous alloy powder with lower coercive force and higher magneticpermeability compared with Comparison 1. Magnetic properties ofcomposition 10 deteriorate because of crystallization; coercive force ofalloy with other compositions (except 10 and Comparison 1) is below 60A/m, the average magnetic permeability is over 35 which is 98% or morethan the magnetic permeability at 100 kHz and 90% or more at 1 MHz,wherein the quality factor is over 40 at 1 MHz.

TABLE 2 Powder characteristic Oxygen Loose packed content density H_(c)Properties of powder core

(ppm) (g/cm³) structure (A/m) μ_(10 kHz) μ_(100 kHz) μ_(1 MHz)Q_(10 kHz) Q_(100 kHz) Q_(1 MHz) 1 3500 2.7 amorphous 45 47 47 46 7 3867 2 3500 2.6 amorphous 53 43 43 41 6 32 72 3 2600 2.7 amorphous 40 6060 59 8 35 77 4 3800 2.5 amorphous 40 53 53 53 5 29 66 5 3000 2.7amorphous 26 42 42 42 6 33 75 6 3300 2.6 amorphous 34 39 39 39 4.5 30 697 2800 2.6 amorphous 35 62 62 60 5.5 32 75 8 3900 2.5 amorphous 50 38 3838 4 27 48 9 3500 2.6 amorphous 47 46 46 44 4.5 28 63 10 3200 2.8crystallized 120 8 8 8 5 7 33 Comparative 1 5200 2.3 amorphous 65 35 3535 4.5 27 60

Embodiment 3

In said embodiment, amorphous Fe—Co—Cr—Sn—Al—P—C—B—Si series alloypowder is prepared by water atomization method. The raw materials areFe, Co, Cr, Sn, Al, P—Fe alloy, graphite, B—Fe alloy and Si.

The nominal composition of said embodiment is listed in Table 3. Thelists of glass transition temperature of corresponding alloy,crystallization temperature, melting point, approximate glass transitiontemperature and width of super cooled liquid region are listed in Table3 respectively. As seen from this table, except that composition 20cannot be fully formed into amorphous materials, alloy with othercompositions all has high reduced glass transition temperature. Theminimum is 0.58 and the maximum is 0.60. The width of super cooledliquid region is over 20K.

TABLE 3

3 Alloy composition in atomic No. percentage T_(g)/K T_(x)/K T_(m)/KT_(g)/T_(m) (T_(x) − T_(g))/K 11 Fe₇₀Co₂Cr₂Sn₂Al₄P₁₀C₂B₄Si₄ 705 744 12080.58 39 12 Fe_(68.5)Co₂Cr₁Sn₂Al₇P_(11.5)C₃B₃Si₂ 715 740 1197 0.60 25 13Fe_(68.5)Co₁Cr₅Sn₃Al₂P_(11.5)C₅B₂Si₂ 715 753 1223 0.58 38 14Fe_(69.5)Co₁Cr_(0.5)Sn₁Al₄P₁₃C₂B₃Si₆ 701 738 1183 0.59 37 15Fe_(69.5)Co₂Cr₄Sn₄Al₁P₁₀C₄B₂Si₄ 723 758 1215 0.60 35 16Fe₇₀Co₂Cr₂Sn₁Al₃P₉C₂B₈Si₃ 704 739 1216 0.58 35 17Fe₇₁Co₂Cr₁Sn₂Al₄P₁₀C₂B₄Si₄ 671 724 1204 0.56 53 18Fe_(71.5)Co₅Cr₁Al₂P_(10.5)C₂B₅Si₃ 698 731 1201 0.58 33 19Fe_(72.5)Co₂Cr₂Al₄P_(9.5)C₁B₄Si₅ 701 732 1209 0.58 31 20Fe₇₅Co₃Cr₃Al₃P₈C₂B₂Si₄ — — 1250 — —

In the amorphous alloy powder with the compositions mentioned above, theoxygen content and the loose packed density of amorphous alloy powder of−300 mess are listed in Table 4. As shown in this table, the averageloose packed density of said series alloy is not less than 2.5 g/cm³ andthe average oxygen content is below 3300 ppm, which implies that thealloy has stronger antioxidation properties.

The amorphous alloy powder of −300 mess obtained by screening theamorphous alloy powder with the compositions mentioned above isisothermal annealed for 30 minutes at a temperature of 440° C., whereinannealing process is in vacuum protection. Said amorphous alloy powderuniformly mixes with 1 wt. % of SiO₂ powder, 1.5 wt. % of epoxy resinand 0.3 wt. % of zinc stearate and then the mixture is dried in the helpof alcohol as co-solvent. The molding of magnetic powder core is pressedunder the pressure of 2 GPa. The magnetic powder core is annealed undervacuum situation. The annealing temperature is 440° C. and annealingtime is 60 minutes. The epoxy resin and estrodur compounds are used tospray and paint the surface of magnetic powder core. The thickness ofspray painting layer is 100 μm.

The properties of amorphous alloy magnetic powder core prepared by saidmethod mentioned above are also listed in Table 4. It can be seen fromTable 4 that, except that composition 20 is in a crystallization processand properties of magnetic powder core deteriorate, other compositionsall have more excellent magnetic properties and magnetic permeability isnot less than 45.

The coercive force of alloy with other compositions (except 10 andComparison 1) is below 60 A/m, the average magnetic permeability is over35 which is 98% or more than the magnetic permeability at 100 kHz and90% or more at 1 MHz, wherein the quality factor is over 60 at 1 MHz.

TABLE 4 Powder characteristic Oxygen Loose packed Properties of powdercore content density H_(c) No. (ppm) (g/cm³) structure (A/m) μ_(10 kHz)μ_(100 kHz) μ_(1 MHz) Q_(10 kHz) Q_(100 kHz) Q_(1 MHz) 11 2600 2.8.0Amorphous 46 48 48 47 7 34 72 12 2900 2.9 Amorphous 37 60 60 58 8 38 8513 2500 2.8 Amorphous 40 65 65 64 7 35 80 14 3000 2.8 Amorphous 41 65 6564 6 33 75 15 2700 2.6 Amorphous 49 60 60 59 6 30 72 16 2800 2.6Amorphous 50 53 53 52 6 32 75 17 3300 2.5 Amorphous 47 49 49 48 5 27 6418 3000 2.7 Amorphous 54 45 45 44 4.5 28 68 19 3200 2.7 Amorphous 52 4646 45 4.5 28 67 20 2800 2.7 crystallized 118 12 12 12 5 7 34

Embodiment 4

In said embodiment, amorphous Fe—Co—Ni—Sn—Al—P—C—B—Si series alloypowder is prepared by non-vacuum gas atomization method. The rawmaterials are Fe, Co, Ni, Cr, Sn, Al, P—Fe alloy, graphite, B—Fe alloyand Si.

The nominal compositions of said embodiment are listed in Table 5. Thelists of glass transition temperature of corresponding alloy,crystallization temperature, melting point, approximate glass transitiontemperature and width of super cooled liquid region are also listed inTable 5 respectively. As shown in this table, except that composition 25cannot be fully formed into amorphous materials, alloy with othercompositions of said series alloy all has high reduced glass transitiontemperature. The minimum is 0.58 and the maximum is 0.60. The width ofsuper cooled liquid region is over 20K.

TABLE 5 Series Compositions of alloy by atomic No. percentage T_(g)/KT_(x)/K T_(m)/K T_(g)/T_(m) (T_(x) − T_(g))/K 21 Fe₇₁Co₂Sn₂Al₄P₁₀C₂B₅Si₄703 740 1208 0.58 37 22 Fe₇₁Ni₂Cr₁Al₄P₁₁C₂B₆Si₂ 715 745 1197 0.60 30 23Fe_(72.5)Co₁Ni₁Sn₃Al₂P_(11.5)C₅B₂Si₂ 708 746 1223 0.58 38 24Fe₆₃Ni₃Co₃Cr_(0.5)Al₄P₁₃C₂B₃Si₆ 720 743 1183 0.61 23 25Fe₆₃Ni₅Co₃Cr₂Sn₄Al₁P₁₀C₄B₂Si₄ — — 1215 — —

In the amorphous alloy powder with the components mentioned above, theoxygen content and the loose packed density of amorphous alloy powder of−350 mess are given in Table 6. As can be seen in this table, theaverage loose packed density of said series alloy is not less than 3.6g/cm³ and the average oxygen content is below 2000 ppm.

The amorphous alloy powder of −350 mess obtained by screening theamorphous alloy powder with the composition mentioned above isisothermal annealed for 30 minutes at a temperature of 400° C., whereinannealing process is in vacuum protection. Said amorphous alloy powderuniformly mixes with 1 wt. % of SiO₂ powder, 2 wt. % of epoxy resin and0.3 wt. % of zinc stearate and then the mixture is dried in the help ofalcohol as co-solvent. The molding of magnetic powder core is pressedunder the pressure of 2.4 GPa. The magnetic powder core is annealedunder vacuum situation. The annealing temperature is 440° C. andannealing time is 60 minutes. The epoxy resin and estrodur compounds areused to spray and paint the surface of magnetic powder core. Thethickness of spray painting layer is 100 μm.

The properties of amorphous alloy magnetic powder core prepared by saidmethod mentioned above are given in Table 6. It can be concluded fromTable 6 that, except that composition 25 is in a crystallization processand properties of magnetic powder core deteriorate, the coercive forceof alloy with other components is below 40 A/m, the average magneticpermeability is over 60 which is 98% or more than the magneticpermeability at 100 kHz and 90% or more at 1 MHz, wherein the qualityfactor is over 60 at 1 MHz.

TABLE 6 Oxygen Loose packed Series content density H_(c) No. (ppm)(g/cm³) Structure (A/m) μ_(10 kHz) μ_(100 kHz) μ_(1 MHz) Q_(10 kHz)_(Q100 kHz) Q_(1 MHz) 21 1500 3.6 amorphous 32 72 72 70 9 45 98 22 12003.7 amorphous 28 70 70 68 9 40 88 23 1250 3.7 amorphous 26 68 68 66 9 4092 24 1100 3.7 amorphous 25 75 75 73 9 41 96 25 800 3.7 crystallization68 13 13 13 6 9 42

Embodiment 5

Amorphous alloy powder is prepared by the same method as embodiment 1.The procedures for preparing magnetic powder core are also the same. Theonly difference is the change of temperature of heat treatment.

FIG. 7 shows the dependence of magnetic permeability on annealingtemperature at 100 kHz. As shown in the figure, the magneticpermeability of said magnetic powder core increases with the increasingof the temperature of heat treatment and the maximum value is obtainedat 440° C., then the magnetic permeability decreases with the increasingof annealing temperature. The maximum magnetic permeability is about 50.

FIG. 8 shows the dependence of quality factor on annealing temperatureat 100 kHz and 1 MHz.

The dependence of the quality factor on annealing temperature is similarto that of magnetic permeability. The difference is that the maximumquality factor of magnetic powder core appears under the annealingtemperature of 380° C. The maximum quality factor is about 75 at 100kHz; the maximum quality factor is about 35 at 1 MHz.

FIG. 9 shows the dependence of coercive force H_(c) on annealingtemperature corresponding to the static magnetic hysteresis loop ofmagnetic powder core under maximum magnetic field of 2000 A/m. As shownin the figure, the change trend of coercive force is completely oppositeto that of magnetic permeability and the minimum coercive force is about44 A/m.

1. A method for making an amorphous magnetic powder core exhibiting excellent soft magnetic properties in high frequency range characterized in that the process includes the following steps: (a) Using an amorphous alloy powder exhibiting excellent soft magnetic properties in high frequency range characterized by a composition in atomic percent of the following formula: (Fe_(1-x)M_(x))_(100-a-b-c)P_(a)T_(b)D_(c), wherein M represents at least one element of Co and Ni; T is over three elements selected from Al, C, B and Si, D is at least one element selected from Sn, Cr, Mn, Mo, W, V, Nb, Ta, Ti, Zr, Hf, Pt, Pd and Au, the subscripts x, a, b, and c satisfy the relationships of 0.0≦x≦0.16, 8≦a≦15, 10≦b≦25 and 0.5≦c≦6 and a required content of insulating agent, adhesives and lubricants, mixing themof and then drying them to obtain dry powder, (b) Compacting said dried powder in a mold under a pressure of 500 MPa-3000 MPa to form a magnetic powder core, (c) Annealing said molded magnetic powder core below the crystallization temperature of said amorphous alloy.
 2. The method for making amorphous magnetic powder core according to claim 1, further comprising after step (c), (d) spray painting magnetic powder core and (e) testing the properties of magnetic powder core.
 3. The method for making amorphous magnetic powder core according to claim 1, characterized in that in step (c), the temperature for annealing said magnetic powder core is between (T_(x)-100° C.) and T_(x), wherein T_(x) represents crystallization temperature; annealing time is from 5 minutes to 300 minutes, the atmosphere is one of vacuum, nitrogen and argon.
 4. The method for making amorphous magnetic powder core according to claim 1, characterized in that in step (c), the annealing temperature is between (T_(x)-70° C.) and (T_(x)-20° C.), wherein T_(x) represents crystallization temperature of said alloy.
 5. The method for making amorphous magnetic powder core according to claim 1, characterized in that the magnetic properties of magnetic powder core obtained shall satisfy the requirements of at least one, or the combination of the following: Magnetic permeability is no less than 35; Quality factor Q is not less than 30 at 1 MHz; Per unit initial permeability is not less than 98% at 100 kHz, not less than 90% or more at 1 MHz; Coercive force H_(c) corresponding with static magnetic hysteresis loop in maximum magnetic field of 2000 A/m is less than 70 A/m. 